My w-4 i opted single 1/0.I want the most federal taxes taken out. I get paid weekly. I've noticed fed taxs are not being taken out if I make less than 250 . Why though?

I'm curious why my federal taxes are not being withheld if I make under $250.00 a week. What do I need to do to rectify this and have federal taxes withheld at a straight rate like they usually are . This is my 1st time getting paid weekly so I'm assuming this might affect it I'm not sure I don't want to choose to withhold extra federal taxes off my weekly check I just want my checkto be taxed the way it's supposed to be for each dollar made. My state / social security/ and Medicare taxs are way above my federal taxes and im reluctant to say I just never noticed before